Determination of mercury in size-segregated ambient particulate matter using CVAAS

A miniaturized flow batch chemical vapor generation system for Hg determination in fish by ICP-MS

A new flow batch (FB) system for chemical vapor generation (CVG) is proposed for mercury (Hg) determination in fish. An inductively coupled plasma mass spectrometer was used as a detector. Low-cost peristaltic mini pumps were used to propel the solutions and different configurations of FB systems (reactor/gas/liquid separator) were studied. The proposed configuration of the FB-CVG system allows good sensitivity, low limit of detection (LOD) and low consumption of reagents and sample solutions. In summary, only 1 mL of reductant, 1 mL of acid and 0.16 mL of sample are needed. The proposed method has good linearity, precision (better than 5 %), LOD of 0.008 μg g-1 and LOQ of 0.012 μg g-1, and high sample throughput, allowing 90 measurements/h. The accuracy of the method was evaluated through the analysis of a certified reference material (DOLT-4 Dogfish Liver), whose result is in good agreement with certified value (t-test with 95 % confidence level) and the quantification limit meets current legislations, of 1.0 μg g-1 (Brazil) and 0.3 μg g-1 (EU). In addition, analyte recovery test was done, where Hg recovery was better than 95 %, demonstrating the good analytical performance of the method. To demonstrate the applicability of the method, five samples of fish tissue (muscle) were analyzed. The proposed FB-CVG system, in addition to being low cost, is robust and requires only the volume of reagents necessary for Hg vapor generation, producing a very low amount of waste. It can be concluded that the proposed system can be used for routine analysis for Hg determination in fish tissue. It is worth noting that with the appropriate adjustments, the system can be coupled to different Hg detectors.

Atmospheric particulate-bound mercury (PBM10) in a Southeast Asia megacity: Sources and health risk assessment

Particulate-bound mercury (PBM) is a global environmental concern owing to its large dry deposition velocities and scavenging coefficients, both of which drive Hg into terrestrial and marine ecosystems. PBM observation studies have been widely conducted over East Asia, but comparable studies in Peninsular Southeast Asia (PSEA) remain scarce. This is the first study reporting PBM concentrations for Ho Chi Minh City (HCMC), the biggest metropolitan area in Vietnam. A total of 222 samples were collected in 2018 and contained an average PBM₁₀ (particulate matter - PM with diameter ≤10 μm) concentration and Hg mass fraction (i.e. PBM/PM) of 67.3 ± 45.9 pg m^-3 and 1.18 ± 1.12 μg g^-1, respectively. Although PBM concentration was lower than those reported in Chinese megacities, the Hg mass fraction was similar to those in China, suggesting strong enrichment from anthropogenic Hg emissions in HCMC. Traffic-induced particulate emission and deposition processes were major factors governing PBM temporal variation at our site. In addition, the prevailing southwest monsoon winds brought air masses that passed through industrial areas and were associated with a higher Hg mass fraction. Statistically significant positive correlations (R² = 0.11-0.52, p < 0.01) were observed for PBM with PM and the Hg mass fraction, indicating similar PM and Hg sources or oxidized Hg adsorption onto PM via gas-particle partitioning. Moreover, PCA results revealed a higher contribution of primary sources than secondary sources to PBM concentration variability in HCMC. A health risk assessment indicated that the PBM concentrations at HCMC posed minimal non-carcinogenic risks (HI < 1) for children and adults, but dermal contact may act as an important exposure route since lightweight clothing is common among residents. This PBM dataset over PSEA, a region with high atmospheric Hg emissions, provides a valuable resource for the Hg scientific community to improve our understanding of Hg biogeochemical cycle.

Source identification of atmospheric particle-bound mercury in the Himalayan foothills through non-isotopic and isotope analyses

This study reports on the sources of atmospheric particle-bound mercury (HgP) in less studied regions of Nepal based on the analysis of stable mercury (Hg) isotopes in aerosol samples from two neighboring areas with high and low anthropogenic emissions (Kathmandu and Dhulikhel, respectively) during 2018. Although the Indian monsoon and westerlies are generally regarded as the primary carriers of pollutants to this region via the heavily industrialized Indo-Gangetic Plain, the concentrations of total suspended particles (TSP) and HgP in Kathmandu were higher than those in Dhulikhel, thus suggesting a substantial contribution from local sources. Both isotopic (δ²⁰⁰Hg and Δ¹⁹⁹Hg) and non-isotopic evidence indicated that dust, waste burning, and industrial byproducts (without Hg amalgamation) were the major sources of Hg in Kathmandu during the study period. Mercury may have been transported via air masses from Kathmandu to Dhulikhel, as indicated by the similar organic carbon/elemental carbon ratios and seasonal trends of TSP and HgP in these two locations. Local anthropogenic sources were found to contribute significantly to atmospheric Hg pollution through dust resuspension. Therefore, dust resuspension should be considered when evaluating the long-range transport of air pollutants such as Hg, particularly in anthropogenically stressed areas.

A Review on Atmospheric Analysis Focusing on Public Health, Environmental Legislation and Chemical Characterization

Atmospheric pollution has been considered one of the most important topics in environmental science once it can be related to the incidence of respiratory diseases, climate change, and others. Knowing the composition of this complex and variable mixture of gases and particulate matter is crucial to understand the damages it causes, help establish limit levels, reduce emissions, and mitigate risks. In this work, the current scenario of the legislation and guideline values for indoor and outdoor atmospheric parameters will be reviewed, focusing on the inorganic and organic compositions of particulate matter and on biomonitoring. Considering the concentration level of the contaminants in air and the physical aspects (meteorological conditions) involved in the dispersion of these contaminants, different approaches for air sampling and analysis have been developed in recent years. Finally, this review presents the importance of data analysis, whose main objective is to transform analytical results into reliable information about the significance of anthropic activities in air pollution and its possible sources. This information is a useful tool to help the government implement actions against atmospheric air pollution.

Particulate and particulate-bound mercury concentrations and size distributions as related to seasonal variations during peak demand/non-peak demand periods

The particulate size distributions of aerosol pollutants (particulates and Hg(p)) at a mixed site were measured and their seasonal variations identified. Atmospheric particulates and the Hg(p) mass median diameter (m.m.d.) were obtained. Hg(p) concentrations increased by approximately 20% during the peak demand period for all particle sizes (18, 10, 2.5, 1 and 0.3 μm). The mean percentage concentration of Hg(p) was highest in summer and followed the order summer > spring > winter > autumn for all particle sizes. Hg(p) concentration exhibited increased from 2004 to 2019.

Inhalation Exposure to Gaseous and Particulate Bound Mercury Present in the Ambient Air over the Polluted Area of Southern Poland

This study concerns the concentrations of gaseous and particle-bound mercury present in ambient air of two Polish sites, differing in terms of emission structure, and the estimation of inhalation risks related to those Hg species. The measurements of total gaseous mercury (TGM) and PM_2.5-bound mercury (PBM) were performed at an urban station in Zabrze and a rural station in Złoty Potok, in 2014–2015. Both sites are located in Silesia, considered one of the European air pollution hot-spots. TGM was measured on-line (Tekran 2537). PM_2.5 samples were taken with the use of low volume samplers. Hg contents in PM were determined by the CVAAS method following thermal decomposition. The median concentrations of TGM and PBM in Zabrze were 2.48 ng m⁻³ and 37.87 pg m⁻³, respectively; meanwhile in Zloty Potok, these were 1.69 ng m⁻³ and 27.82 pg m⁻³, respectively. Clearly, seasonal variability of TGM and PBM concentrations were observed, reflecting the importance of Hg and PM emissions from coal combustion for power and heating purposes. Health risk assessment was performed using a deterministic approach by the most conservative exposure scenario. The obtained HQ ratios and the cumulative HI indexes were below the limit value (<1). This means an unlikely health hazard due mercury inhalation.

Development of methodology to generate, measure, and characterize the chemical composition of oxidized mercury nanoparticles

The phase of oxidized mercury is critical in the fate, transformation, and bioavailability of mercury species in Earth's ecosystem. There is now evidence that what is measured as gaseous oxidized mercury (GOM) is not only gaseous but also consists of airborne nanoparticles with distinct physicochemical properties. Herein, we present the development of the first method for the consistent and reproducible generation of oxidized mercury nano- and sub-micron particles (~ 5 to 400 nm). Oxidized mercury nanoparticles are generated using two methods, vapor-phase condensation and aqueous nebulization, for three proxies: mercury(II) bromide (HgBr₂), mercury(II) chloride (HgCl₂), and mercury(II) oxide (HgO). These aerosols are characterized using scanning mobility and optical sizing, high-resolution scanning transmission electron microscopy (STEM), and nano/microparticle interface coupled to soft ionization mercury mass spectrometric techniques. Synthetic nanoparticle stability was studied in aqueous media, and using a microcosm at ambient tropospheric conditions of ~ 740 Torr pressure, room temperature, and at relative humidity of approximately 20%. Analysis of microcosm airborne nanoparticles confirmed that generated synthetic mercury nanoparticles retain their physical properties once in air. KCl-coated denuders, which are currently used globally to measure gaseous mercury compounds, were exposed to generated oxidized mercury nanoparticles. The degree of synthetic mercury nanoparticle capture by KCl-coated denuders and particulate filters was assessed. A significant portion of nanoparticulate and sub-micron particulate mercury was trapped on the KCl-coated denuder and measured as GOM. Finally, we demonstrate the applicability of soft ionization mercury mass spectrometry to the measurement of mercury species present in the gaseous and solid phase. We recommend coupling of this technique with existing methodology for a more accurate representation of mercury biogeochemistry cycling. Graphical Abstract.

Dendrograms, heat maps and principal component analysis - the practical use of statistical methods for source apportionment of trace elements in PM10

Dendrogram (DE), heat map (HM) and principal component analysis (PCA) methods were used in order to identify possible emission sources of As, Cd, Co, Cr, Hg, Mn, Ni, Pb, Sb and Se in ambient PM10 collected in the surroundings of working power plants. Each statistical tool resulted in slightly different clusters. The best approximation of possible emission sources was received by the use of statistical analysis of trace-element concentrations combined with characterization of the sampling sites. In the study, PCA was indicated as the most useful statistical tool for source apportionment of trace elements in PM10. Major sources identified by PCA included: (1) coal combustion, (2) soil and road-dust resuspension, (3) the use of pesticides and (4) waste incineration.

The Existence of Airborne Mercury Nanoparticles

Mercury is an important global toxic contaminant of concern that causes cognitive and neuromuscular damage in humans. It is ubiquitous in the environment and can travel in the air, in water, or adsorb to soils, snow, ice and sediment. Two significant factors that influence the fate of atmospheric mercury, its introduction to aquatic and terrestrial environments, and its bioaccumulation and biomagnification in biotic systems are the chemical species or forms that mercury exists as (elemental, oxidized or organic) and its physical phase (solid, liquid/aqueous, or gaseous). In this work, we show that previously unknown mercury-containing nanoparticles exist in the air using high-resolution scanning transmission electron microscopy imaging (HR-STEM). Deploying an urban-air field campaign near a mercury point source, we provide further evidence for mercury nanoparticles and determine the extent to which these particles contain two long suspected forms of oxidized mercury (mercuric bromide and mercuric chloride) using mercury mass spectrometry (Hg-MS). Using optical particle sizers, we also conclude that the conventional method of measuring gaseous oxidized mercury worldwide can trap up to 95% of nanoparticulate mercuric halides leading to erroneous measurements. Finally, we estimate airborne mercury aerosols may contribute to half of the oxidized mercury measured in wintertime Montréal urban air using Hg-MS. These emerging mercury-containing nanoparticle contaminants will influence mercury deposition, speciation and other atmospheric and aquatic biogeochemical mercury processes including the bioavailability of oxidized mercury to biota and its transformation to neurotoxic organic mercury.

Atmospheric PM2.5 Mercury in the Metropolitan Area of Mexico City

In this study, atmospheric mercury concentration in airborne particulate matter with an aerodynamic diameter ≤ 2.5 µm (PM_2.5) was analyzed by ICP-MS. Samples were collected in the Mexico City Metropolitan Area (MCMA), during 2013, in five locations, Northwest, Northeast (NE), Central, Southwest and Southeast, along three seasons: dry warm, rainy, and dry cold (DC). It can be observed that NE shows the highest mercury concentration (p < 0.05), where pollution events were identified. The seasonal distribution shows that samples collected during DC present the highest concentration (p < 0.05). These results are in agreement with the distribution of important mercury industrial sources located in the northern urban area as well with the temperature and wind conditions during 2013. The comparison of data obtained in this work with those of similar previous studies clearly indicates a decrease, between 2006 and 2013, of mercury content in PM_2.5 collected in MCMA.

Magnetic susceptibility of spider webs as a proxy of airborne metal pollution

The purpose of this pilot study was to test spider webs as a fast tool for magnetic biomonitoring of air pollution. The study involved the investigation of webs made by four types of spiders: Pholcus phalangioides (Pholcidae), Eratigena atrica and Agelena labirynthica (Agelenidae) and Linyphia triangularis (Linyphiidae). These webs were obtained from outdoor and indoor study sites. Compared to the clean reference webs, an increase was observed in the values of magnetic susceptibility in the webs sampled from both indoor and outdoor sites, which indicates contamination by anthropogenically produced pollution particles that contain ferrimagnetic iron minerals. This pilot study has demonstrated that spider webs are able to capture particulate matter in a manner that is equivalent to flora-based bioindicators applied to date (such as mosses, lichens, leaves). They also have additional advantages; for example, they can be generated in isolated clean habitats, and exposure can be monitored in indoor and outdoor locations, at any height and for any period of time. Moreover, webs are ubiquitous in an anthropogenic, heavily polluted environment, and they can be exposed throughout the year. As spider webs accumulate pollutants to which humans are exposed, they become a reliable source of information about the quality of the environment. Therefore, spider webs are recommended for magnetic biomonitoring of airborne pollution and for the assessment of the environment because they are non-destructive, low-cost, sensitive and efficient.

PM Origin or Exposure Duration? Health Hazards from PM-Bound Mercury and PM-Bound PAHs among Students and Lecturers

This study assessed inhalation exposure to particulate matter (PM₁)-bound mercury (Hg_p) and PM₁-bound polycyclic aromatic hydrocarbons (PAHs) among university students. For this purpose, simultaneous indoor (I) and outdoor (O) measurements were taken from two Polish technical universities (in Gliwice and Warsaw) located in distinct areas with respect to ambient concentrations and major sources of PM. The indoor geometric mean concentrations of Hg_p were found to be 1.46 pg·m⁻³ and 6.38 pg·m⁻³ in Warsaw and Gliwice, while the corresponding outdoor concentrations were slightly lower at 1.38 pg·m⁻³ and 3.03 pg·m⁻³, respectively. A distinct pattern was found with respect to PAH concentrations with estimated I/O values of 22.2 ng·m⁻³/22.5 ng·m⁻³ in Gliwice and 10.9 ng·m⁻³/11.12 ng·m⁻³ in Warsaw. Hazard quotients (HQs) as a result of exposure to Hg_p for students aged 21 ranged from 3.47 × 10⁻⁵ (Warsaw) to 1.3 × 10⁻⁴ (Gliwice) in terms of reasonable maximum exposure (RME). The non-cancer human health risk value related to Hg_p exposure was thus found to be below the acceptable risk level value of 1.0 given by the US EPA. Daily exposure values for lecture hall occupants, adjusted to the benzo(a)pyrene (BaP) toxicity equivalent (BaP_eq), were 2.9 and 1.02 ng·m⁻³ for the Gliwice and Warsaw students, respectively. The incremental lifetime cancer risk (ILCR) values with respect to exposure to PM₁-bound PAHs during the students’ time of study were 5.49 × 10⁻⁸ (Warsaw) and 1.43 × 10⁻⁷ (Gliwice). Thus, students’ exposure to indoor PAHs does not lead to increased risk of lung cancer.

Characterizations of atmospheric particulate-bound mercury in the Kathmandu Valley of Nepal, South Asia

The Kathmandu Valley, located in the Himalayan foothills in Nepal, is heavily polluted. In order to investigate ambient particulate-bound mercury (Hg) in the Kathmandu Valley, a total 64 total suspended particulates (TSP) samples were collected from a sub-urban site in the Kathmandu Valley, the capital region of Nepal during a sampling period of an entire year (April 2013-April 2014). They were analyzed for ambient particulate-bound Hg (PBM) using thermal desorption combined with cold vapor atomic spectroscopy. In our knowledge, it is the first study of ambient PMB in the Kathmandu Valley and the surrounding broader Himalayan foothill region. The average concentration of PBM over the entire sampling period of a year was found to be 850.5 (±962.8) pg m^-3 in the Kathmandu Valley. This is comparable to those values reported in the polluted cities of China and significantly higher than those observed in most of urban areas in Asia and other regions of world. The daily average Hg contents in TSP (PBM/TSP) ranges from 269.7 to 7613.0ngg^-1 with an average of 2586.0 (±2072.1) ng g^-1, indicating the high enrichment of Hg in TSP. The average concentrations of PBM were higher in the winter and pre-monsoon season than in the monsoon and post-monsoon season. The temporal variations in the strength of anthropogenic emission sources combined with other influencing factors, such as ambient temperature and the removal of atmospheric aerosols by wet scavenging are attributable to the seasonal variations of PBM. The considerably high dry deposition flux of PBM estimated by using a theoretical model was 135μgm^-2yr^-1 at the Kathmandu Valley. This calls for an immediate attention to addressing ambient particulate Hg in the Kathmandu Valley, including considering it as a key component of future air quality monitoring activities and mitigation measures.